I.V. systems have generally been of two basic types, one, a gravity feed system in which a collapsible fluid reservoir located in an elevated position is connected to the patient through a manually adjustable valve, and two, a system in which the fluid is physically pumped at an adjustable rate of flow and pressure to the patient. In the first system the feed pressure is limited, while the second system is relatively complex and expensive to manufacture and to maintain. While the use of a pump enables the feeding of fluids under high pressure to the arteries of a patient the pump must be powered by electricity which has restricted its use.